China will also reduce annual carbon dioxide emissions from coal-fired power generation by 180m tonnes by 2020, the official People’s Daily website said. It did not give comparison figures or elaborate how it would achieve the result.

The smog was caused by “unfavourable” weather, the Ministry of Environmental Protection said. Emissions in northern China soar over winter as urban heating systems are switched on and low wind speeds meant that polluted air does not get dispersed.

The hazardous air, which cleared on Wednesday, underscores the challenge facing the government as it battles pollution caused by the coal-burning power industry and raises questions about its ability to clean up its economy.

Reducing coal use and promoting cleaner forms of energy are set to play a crucial role in China’s pledges to bring its climate warming greenhouse gas emissions to a peak by around 2030.

China’s delegate at the Paris talks, Su Wei, “noted with concern” what he called a lack of commitment by the rich to make deep cuts in greenhouse gas emissions and help developing nations with new finance to tackle global warming.